Digi PH meter

[modsquad09]

Will any basic meter found at hydroponic stores work? Or is higher price gonna do me any better?

right now i have ph papers, but i want to be as accurate as possible and it hard to tell the color on those towards the end.

Anything to look for when shopping for one? do i have to get a special one to handle the corrosive materials like HDPE?
Thanks

 

[benzyme]

don't worry about corrosive materials, most calomel electrodes are meant to be placed in strong acids and bases, though I'm not familiar with the meters found at hydroponics stores.
those may have a narrow pH range

like anything else, you get what you pay for. despite this general rule, one can find decent deals on a certain auction site, because some people just liquidate assets of closed labs, and have no idea what instruments are worth.

the brands to look out for are Hanna (most common entry level meter), VWR, Beckman, Thermo/Orion, Corning, and Milwaukee. Ones with a BNC connector are quite common, you just need to replace the electrode when it goes bad. These things need to be calibrated often, so make sure you get buffers along with your meter; pH 4 and pH 7 are common, but some meters have three calibration points, 4, 7, and 10.

 

[DudeMeetTyler]

i had a pH meter from a hydro store.. spent 160 on it with 4 and 7 buffers, also calibrated at 10, though i didnt the 10 buffer at the time..

seemed to work fine for a while until buddy (not me) stored it upside down and the cap was not liquid tight and all the storage solution ran out and the electrode dried out. not sure how long it was like this for but it has not worked since (gives reading which are completely off)

 

[benzyme]

I got an Orion 230A for $30, they list for $300 or more; they're used extensively in the field for EPA water testing.
electrodes can run from $19.99 to over $250. they are what are considered "consumables", and are meant to be replaced;
9 times out of 10, the variability in measurements are from the electrode, not the meter.

 

[smokerx]

Dont worry about those expensive once unless you serious about it as benzyme I have this one and it works very well

 

[benzyme]

there ya go
for all practical purposes, one like that is all you need, along with some pH buffers.


to test measurement, here's what I did:

-find a bottle of vinegar, and look for the % acidity.

-enter that value into wolframalpha as "__% acetic acid";
look for the result it gives in N (normality) or M (molarity).

-enter that value into the search bar as "__ N (or M) acetic acid"; you will get a result
which tells you what the calculated pH is.

-pour a small amount of vinegar into a shot glass, just enough to immerse the electrode in.
measure the pH and compare its value to the one obtained from wolframalpha. If your meter is calibrated, it should match up closely

try the same with household ammonium hydroxide (the bottle may tell you % base, or % ammonium hydroxide), so you can test the accuracy at the higher end of the pH scale.

 

[DudeMeetTyler]

thats the one i bought, only 60 bucks on amazon.. gotta love those retail mark ups..

http://www.amazon.com/Oakton-Waterproof-EcoTestr-pH1/dp/B002OC7EYM

@benz
so your saying i can simply replace the electrode? any thoughts on how?
(as i have just been using the measurements from my notes that have worked before but it would be nice to be sure)

Thanks

 

[benzyme]

not familiar with that particular model, though I had a Hanna pH pen-type meter that looked similar. it had two probes, a glass electrode for testing pH, and a metal one for measuring temp. it came with a tool to twist off the pH electrode, which was replaceable and retailed for 39.99 - 49.99.

but that oakton meter (and the ebay meter) looks like they're completely integrated with no user replaceable parts, sort of like a mac laptop :lol: . are there at least screws near the electrode?

 

[a1pha]

Hey Benz -

I've been eyeing this unit. Do you have any opinion on it?

Thank you!

 

[benzyme]

looks pretty good
never heard of that brand, but it has the features you want in
a meter: auto-calibration, 2 or 3 pt. calibration, and replaceable electrode.

 

[DudeMeetTyler]

no screws or anything,

even getting into the battery compartment is tricky.. looks like im sol on this one..

thanks for the reply though